Hello. I think, Its impossible to simulate crack grows using only beam elements.

May be you should use 3d elements, or using sub-modeling approach.

It is impossible to simulate the crack propagation using meso-scale model using beam elements. Beside you have to be extra carful about element size and fracture energy. Personally I don't recommend meso scale model for crack propagation. Please read my article "Flexural and Interfacial Behavior of FRP-Strengthened Reinforced Concrete Beams". You can find detailed discussion about meso-scale model and crack propagation simulation.